Would you buy ME:A if it were on Steam or GOG?

Why should I? Origin is less invasive than Steam and also doesn't force me to download useless crap. Gog is still the best but Origin isn't all that bad.

I couldn't care less about which client it's on; I'll be buying from whoever has it cheapest.

Also, someone mentioned some things they'd heard about Origin and listed refund policies. I bought a game once and super hated it, asked for a refund and it was processed in less than an hour. And they refunded straight to my credit card too, not this steam wallet bullshit. Maybe others have had issues, but other than the fact that they won't sell original ME trilogy DLC for cash instead of points, I don't have an issue with them.

Lucky you.
Sad for those of us allergic to chocolate. 

As much as I love steam, I need to have Origin for things like Battlefield, so as long as that's there I'm fine with using it. Steam is getting a bit dated with its content delivery, and it is way too full of games these days. I'm definitely starting to like Steam less.

Oh I highly doubt ME:A will come to GOG unless GOG is okay with it having DRM. EA's big titles are using Denuvo because it allows them to have nearly uncrackable games without resorting to the issues with online-only titles.

I usually now game on console but when I game on PC, I buy everything I can from GoG. Despite playing it for PS4, I also bought an extra copy of TW3 on GoG for PC (even though I never going to use it) just to show my support for GoG gaming "philosophy" and CDPR as a company.

If ME:A was available on GoG, I would do the exact same thing.

I'd love to have it on GOG but I don't really care about Steam vs Origin. DRM is still DRM.

I also don't really understand why Valve gets such a free pass from gamers. They're a big money-hungry corporate machine too, and they act like it. They're simply more subtle than EA.

Just last year in Australia they were found guilty of misleading and deceptive conduct for telling Steam users that they weren't entitled to a refund when in fact they were by law. I've also seen them do some pretty dodgy stuff re pricing and advertising discounts (e.g. bumping up the price of a game right before a sale so that the sale price can be advertised as a bigger discount).

Most of the negative stuff I've heard about Origin is just about it being a clunky, buggy platform. I'd probably prefer that to sneaky practices.

so EA thinks denuvo drm is bulletproof huh? well i can bet you dime to a dollar that someone will find a way to crack it. even if EA introduces a new version it's gonna get cracked eventually. Hackers always love a good challenge. EA is just wasting time, energy and money on an idea that does more harm than good.  one time when i was perusing thru Pirate Bay I found that someone manage to crack DAI's drm(they even managed to bypass the whole using origin program thing!). I wouldn't be surprised that someone will crack ME:A's drm eventually. it's inherently a dumb idea and i don't understand why EA remains so persistent to the idea.
EA thinks their games are safe and secure from any kind of "tampering" they are dumb
hackers WILL find a way, they always do...

They don't care if the game will be cracked eventually, what they want is that the game remained uncracked during the first weeks when most of the sales are made. 

Regardless, I always purchase a physical copy. So whether I load it up through Origin, Steam, or whatever makes no difference. I do like steam from the stand point of easily installing mods, but the lack of quality content and access to DLC's in many cases makes it a deal breaker.

Bethesda recently removed Denuvo from DOOM (2016). I wonder what their thinking was.

Well, I don't know about the DRM thing (I'm sure a cost-benefit analysis was done,) but MP made them a shit ton full of money so it is not going anywhere.  I used to feel the same about MP, but ME3's combat system being good can be directly tied to the addition of MP, so I'm good with it so long as it doesn't intrude in the SP game.